Starting a fire proved to be the nemesis and success for a Mormon father-son team during this week’s journey and Survival Test on NBC’s “Get Out Alive with Bear Grylls.”

Jim and Austin Vach, of the Maple Valley Washington Stake of The Church of Jesus Christ of Latter-day Saints, struggled to make fire with a bow and drill during the journey but were successful in making and carrying it during the Survival Test, which they won giving them immunity from elimination. They are now in the final four teams and in contention for the show’s $500,000 grand prize.

“How you perform on each of these journeys is critical,” Grylls reminded the group as they gathered before the journey through New Zealand’s South Island.

This week’s journey has the remaining five teams scaling down a steep, craggy cliff using rappelling gear, navigating around Storm Creek to find food and then going to the night’s camp.

The teams drew knives with a task written on the blade at the beginning of each journey.

Jim and Austin Vach were last to draw and got the “Fire” knife with the responsibility to build fire with a bow and drill. Last week, they had fire and successfully built the fire the same way.

They were also given an emergency flint and instructed to get help if they weren’t successful this week.

A father-daughter team from Stillman Valley, Ill., Andrew “Lucky” Larson, 58, and 24-year-old Andrea “Louie” Larson, who is afraid of heights, drew the obstacle knife and were responsible for getting everyone down the cliff safely.

“Bear makes things look very easy,” 61-year-old Jim Vach said of Grylls’ demonstration of getting down the cliff. “For a lot of us, it’s the first time or we've done it very few times, so there is a lot of terror in some of our faces.”

Despite some struggles, all made it down the cliff, including Louie Larson, who faced her fear and was last down.

Then the food teams led the group down the steep and slippery banks downriver to find the dead goat Grylls left for them. Powell’s leg, injured during a motorcycle accident that left him in the hospital for 24 days, was bothering him during part of the hike.

At the campsite, the Vachs struggled to start the fire and worked on it for a couple of hours until after dark when they used the emergency flint. With a fire going, they were able to roast the goat and the fish roux Grylls brought by.

It was one of the coldest nights of the experience, and there was frost on just about everything.

“Of all the teams, we had performed our task the worst, so it is imperative that we win this test,” Austin Vach said.

At the survival test, Grylls told the teams they were all about on equal footing with their abilities.

“You’ve never needed that safety from elimination as much as right now,” Grylls said.

They had to cross the river, through obstacles, make fire using flint and steel and add tinder fungus to carry the fire back across the river, using the tinder fungus to light another fire to be high enough to set a torch on fire.

The Vachs were second to light the first fire behind Wadsworth and Krieger but were first across the river.

“I was just so happy we won in the moment we needed it,” Austin Vach said.